Physiological and molecular biological studies on the pathogenesis of impaired insulin secretion in diabetes mellitus.

作为非胰岛素依赖型糖尿病（NIDDM）的主要病理生理特征之一，葡萄糖诱导的胰岛素分泌的选择性损害已被广泛了解。另一方面，胰岛素分泌能力响应于葡萄糖以外的刺激而增强。因此，我们直接采用膜片钳技术研究了电压依赖性Ca^<2+>通道（VDCC）的活性，该通道对细胞内Ca^<2+>水平的调节具有非常重要的作用。用分离的GK大鼠胰岛β细胞，用全细胞记录法记录L型和T型Ca^<2+>通道电流。此外，为了研究在不介导K通道关闭的情况下调节葡萄糖代谢过程中VDCC活性的细胞内机制<ATP>，我们还利用了制霉菌素穿孔膜片法。GK β细胞膜去极化后L型和T型VDCC活性均明显增强。在对照β-细胞中，VDCC活性在穿孔补片中葡萄糖负荷后更增强。然而，在GK β细胞中未发现这种增加。这些现象似乎与GK大鼠的NIDDM β细胞中发现的胰岛素分泌能力受损的葡萄糖选择性密切相关。

As one of the major characteristics in pathophysiological aspects in noninsulin-dependent diabetes mellitus (NIDDM), the selective impairment of glucose-induced insulin secretion has been well known. On the other hand, the insulin secretory capacity is rather enhanced in response to the stimuli other than glucose. We, therefore, investigated the activity of voltage-dependent Ca^<2+> channel (VDCC) directly using the patch-clamp technique, which has a very important role on the regulation of intracellular Ca^<2+> levels. Using single beta-cells obtained by the dispersion of pancreatic islets of GK rats with genetically NIDDM,the L-and T-types of Ca^<2+> channel currents were recorded by whole cell recording. In addition, in order to investigate the intracellular mechanisms for modulating VDCC activities throuph glucose metabolism without mediating the K_<ATP> channel closure, the perforated patch using nystatin method was also utilized. Both of L-and T-type VDCC activities were found to be significautly enhanced after the membr anedepolarization in GK beta-cells when compared to the controls. In control beta-cells, the VDCC activities were more augmented after glucose loading in perforated patches. However, such an augmentation was not to be found in GK beta-cells. These phenomena seem to be closely related to the glucose selectivity of the impairment of insulin secretory capacity found in NIDDM beta cells of GK rats.